1. Field of the Invention
The present invention relates to a supermagnetostrictive alloy having a high coefficient of magnetostriction and satisfactory toughness, and more particularly to a super-magnetostrictive alloy which is suitable for use as a primary element of a device designed to convert magnetic energy to mechanical energy and vice versa. Magnetostriction is stress which is caused in a magnetic material by application of an external magnetic field, and has an important application in devices known as a magnetostrictive filter, a magnetostrictive sensor, a magnetostrictive delay line, a magnetostrictive oscillator, etc.
2. Description of the Related Art
One result of recent progress made in instrumentation technology and developments in the field of precision instruments has been the widespread demand for displacement drivers, which are indispensable for the control of micro displacements in the order of microns. A conversion device designed to convert magnetic energy to mechanical energy and vice versa is an example of a device commonly used at present as a driving mechanism of a displacement driver.
An Ni-based alloy, an Fe-Co alloy, a ferrite are examples of conventionally known magnetostrictive materials. However, these examples produce only a small amount of magnetostrictive displacement, and are not suitable for use as the material of a displacement controller or driver required of precision in the order of microns.
U.S. Pat. No. 4,375,372 to Norman Co. Koon et al. discloses a compound obtained from rare earth elements and iron, and U.S. Pat. No. 4,378,258 discloses a compound obtained from rare earth elements and 3d-transition elements. As is suggested in these U.S. patents, an intermetallic compound obtained from rare earth elements and iron produces magnetostriction which is nearly one hundred times as large as the magnetostriction of an Ni-based alloy, and is therefore suitable for producing sufficient magnetostrictive displacement. However, the compounds disclosed in the U.S. Patents do not covert magnetic energy to mechanical energy at high efficiency. In addition, they are fragile, so that they are not suitable for use as the material of a precision displacement controller or driver.
Japanese Patent No. 1370488 to Sahashi et al. (whose are the same inventors as the present invention), discloses that a Laves-phase intermetallic compound formed of a Dy-Tb-Fe-Mn alloy produces saturated magnetostrictive stress (.lambda.s) exceeding 1,000.times.10.sup.-6. However, even the magnetostrictive materials shown in the Japanese Patent do not fully meet practical requirements, namely, the requirement that they produce great stress by application of a magnetic field of several kOe, and the requirement that they be very tough. One of the matters which should be considered when producing micro displacement is that the magnetostrictive characteristic of a magnetostrictive material is dependent, more or less, on the temperature at which the material is used. If the displacement i.e., a change in the magnetostrictive characteristic depends largely on the temperature, problems will arise in practice.